We propose building a 21 pinhole non-rotating SPECT camera, which will acquire views simultaneously, that will be able to do studies either cannot be done or cannot be performed consistently and reliably on current rotational SPECT cameras, which acquires views sequentially. These studies include tomographic first pass, stress studies, and gated cardiac studies. Tomographic first pass studies allow more accurate quantitative measurements (EFs), and allow wall and valve abnormalities to be located more precisely. Gated cardiac studies can be done more reliably when a posteriori beat selection is done, which the list mode acquisition of the 21 pinhole camera allows. Multiple studies can then be made from a single acquisition to study different beta types. The high precision necessary in moving heavy heads adds to the cost of SPECT cameras. Eliminating the movement should substantially reduce the cost, making nuclear cardiac procedures more cost effective. Cost effectiveness can also be increased using a simultaneous dual isotope (Tc-99m & T1-201) protocol. This has the benefit of requiring only a single session to get both stress and rest images. This also makes the procedure more comfortable and convenient to the patient and repositioning artifacts are eliminated. Our 21 pinhole system corrects the downscatter from Tc-99m into the T1-201 window by retaining the entire energy spectrum and using it to estimate the downscatter component. PROPOSED COMMERCIAL APPLICATION: The 21 pinhole SPECT system will be used by cardiologists to perform the following studies: First pass studies; Gated studies (both blood pool and perfusion); stress gated studies; and Perfusion studies. All these studies can be done tomographically, which current systems cannot do for first pass and stress studies. This will be a dedicated cardiac system.